In subjects with heart failure, genetic variation will affect clinical outcomes and the response to therapy. Heart failure is a polygenic disorder, and the impact of specific genetic polymorphisms will be influenced by genetic background. For several genes critical to heart failure pathogenesis, the prevalence of adverse alleles differs significantly between white and black cohorts. The current proposal will enroll one thousand subjects with heart failure due to systolic dysfunction including 500 white subjects and 500 black subjects, and will examine the impact of racial differences in genetic background on left ventricular function and clinical outcomes. Specific Aim 1 will evaluate the impact of genetic background on left ventricular ejection fraction (LVEF) and LV diastolic diameter in 500 black subjects with chronic heart failure and a matched cohort of 500 white subjects. The proposal will focus on adverse alleles of key heart failure mediators including the ACE deletion, aldosterone synthase promoter -344C, NOS3 Asp298, and betal Arg389 variants. Specific Aim 2 will investigate the impact of the adverse alleles from aim 1 on survival in the overall cohort and separately in the black and white subsets. Specific aim 3 will explore gene-gene interactions to examine whether the impact of the ACE D allele is modified by coinheritance of the GNB3 T haplotype. This polymorphism is linked to increased alpha adrenergic activation and low plasma renin and is far more prevalent in black cohorts. Specific Aim 3 will explore in the black heart failure cohort the use of Mapping by Admixture Linkage Disequilibrium (MALD), which utilizes comparisons of genomic DMA of African and European orgin, to determine the potential contributions of genomics to apparent racial differences in remodeling and heart failure outcomes. This proposal will address an important clinical question and will provide an ideal program for mentoring young investigators in the methodologies involved in genetics outcomes research.